ignore idea files
VAADINPNL-16  Change fetching vaadin-version list
Sorting version list (by alphabetically)
VAADINPNL-12  Rollback changes if something wrong during update
Create backups
VAADINPNL-12  Rollback changes if something wrong during update
VAADINPNL-12  Rollback changes if something wrong during update
              Restore files from backup
some improvements
Merge pull request #3 from igor-borisov/master

fetching releases list, rollback feature